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Fizeau's Experiment

  1. Jul 6, 2015 #1
    1. The problem statement, all variables and given/known data
    Angular Speed of the 8 gap wheel Is variable.
    Red Laser (wavelength around 656.6 nm)
    Approximate the length of the traveling ray to the mirror in meters.
    Using the length of the traveling ray, calculate the speed of light.

    2. Relevant equations
    c=lambda*f

    3. The attempt at a solution
    I tried using a simple speed * time * distance equation but it didn't make sense to me.
    I have looked for other similar threads but they are all dealing with different variables like finding out the perfect timing ect.
     
  2. jcsd
  3. Jul 6, 2015 #2

    mfb

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    I think there is something missing in the problem statement.
    I don't think there is any equation where you multiply those three things. Can you show what you actually did?
     
  4. Jul 7, 2015 #3
    upload_2015-7-7_12-40-40.png

    Here is the experiment and all of the data that has been given, when I click start the wheel then begins to turn and cut out the laser as it should in the experiment. Our professor asked us to find the length of the laser and I'm not quite sure how to solve that. Any information or tips would help!
    ( the distance to from the wheel to the mirror is 8.65km)

    Thanks MFB!
     

    Attached Files:

  5. Jul 7, 2015 #4

    SteamKing

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    It's too bad that only a thumbnail was uploaded. I can no more read what's written in this image than I can use my sun glasses to see through walls.

    In any event, have you read up on how Fizeau set up his apparatus and used it to calculate his value of the speed of light?
     
  6. Jul 7, 2015 #5
    Yes I have watched many videos on how he set it up and found his value for the speed of light. I am just unsure about the part where we have to calculate the distance of the laser ray.
     
  7. Jul 7, 2015 #6

    mfb

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    You'll need the angular velocity of the wheel or something similar to find the distance.

    The sketch seems to have a length given there, which would make finding the length a bit pointless.
     
  8. Jul 7, 2015 #7
    In the lab the angular velocity is actually variable to our choosing, and for the length that we are trying to find is actually the length of the laser that has been let in by the turning of the wheel.

    Sorry if there was any confusion.
     
  9. Jul 8, 2015 #8

    mfb

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    Sure, for an actual setup you measure the distance, but as far as I understood you are supposed to calculate it here based on other given quantities. But then you need the angular velocity of the wheel.
     
  10. Jul 8, 2015 #9
    Okay thanks! Any idea on formulas to use with the angular velocity to find the distance? Or where to look for them at?
     
  11. Jul 8, 2015 #10

    mfb

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    Speed is distance traveled divided by time needed, as simple as that.
    The time depends on the angular velocity and the number of holes in the wheel.
     
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